Patent GB-423892-A (GB)
Title: Manufacture of coloured lacquers and coating compositions
IPC: C09B65/00
Filed: 1933-12-18
Abstract: Triarylmethane dyes; azo dyes.--Lacquers and film - forming coating - compositions are coloured by converting a mordant dyestuff of the triarylmethane series or a leuco compound thereof into a chromium compound of the dyestuff by treatment with chromic acid or a salt thereof in the lacquer or composition itself. Lacquers having a basis of acetylcellulose, artificial resins such as Recyl resins or chlorinated rubber, gelatine solutions, spirit lacquers, linseed oil varnishes and printing varnishes may be so coloured, the colourations being especially fast to light.  The following examples are specified, the fast to light colourations being as indicated.  (1) Leuco-Eriochrome azurol B, sodium bichromate and oxalic acid are added to a nitrocellulose lacquer containing collodion wool, butanol, ethyl lactate, butyl acetate, ethyl alcohol, triphenyl phosphate and Sipalin (adipic acid ester) and the whole is gently warmed (blue). (2) The leuco compound of the dyestuff from 2-chloro-4-dimethylaminobenzaldehyde (1 mol.) and o-cresotinic acid (2 mols.) (cf. German Specification 198,729) is added, with sodium bichromate and oxalic acid, to an acetylcellulose lacquer containing acetylcellulose, ethyl lactate, ethyl formate, acetone, triphenyl phosphate and tricresyl phosphate and the whole is gently warmed (violet).  (3) The leuco compound of the dyestuff from 2-chlorobenzaldehyde (1 mol.) and o-cresotinic acid (2 mols.) (cf. German Specification 198,909) is added, with sodium bichromate and oxalic acid, to a chlorinated rubber lacquer containing ethyl lactate, benzene and a solution of chlorinated rubber in chlorobenzene and the whole is gently warmed (blue).  (4) The leuco compound of the dyestuff from 5-(2<1> : 4<1>-dinitrophenyl)amino-2 : 6-dichlorobenzaldehyde (1 mol.) and o-cresotinic acid (2 mols.) (cf. German Specification 235,155) is added, with sodium bichromate and oxalic acid, to a nitrocellulose lacquer and the whole is gently warmed (green).  (5) The leuco compound of the dyestuff from 1 mol. of the azo dye, 5 - amino - 2 : 6 - dichlorobenzaldehyde --> 1-phenyl-3-methyl-5-pyrazolone, and 2 mols. of o-cresotinic acid (cf. Specification 2394/10, [Class 2 (iii)]) is added with sodium bichromate and oxalic acid to an acetylcellulose lacquer and the whole is gently warmed (green). (6) Eriochrome azurol B and sodium bichromate are added to a nitrocellulose lacquer containing collodion wool, butanol, butyl acetate, dibutyl phthalate, tricresyl phosphate and ethyl alcohol and the whole is gently warmed (brilliant clear blue).  (7) Eriochrome azurol B (free acid) is shaken for \ba1/4\be hour with a nitrocellulose lacquer containing collodion wool, butanol, a Recyl resin, a Recyl balsam, ethyl lactate, butyl acetate, acetone and benzene, sodium bichromate is added, and the whole is heated at 40--60 DEG  C. for \ba1/4\be hour (brilliant blue).  (8) The ethyl ester of Eriochrome azurol B and sodium bichromate are added to a nitrocellulose lacquer and the whole is gently warmed (violet). (9) The dyestuff of (3) is added with sodium bichromate to a chlorinated rubber lacquer and the whole is gently warmed (pure blue).  (10) Eriochrome cyanin R (free acid) is added with sodium bichromate to a lacquer containing a Recyl resin, ethyl lactate, toluene and acetone and the whole is gently warmed (reddish blue). (11) Eriochrome geranol R (free acid) is added, with sodium bichromate to a spirit lacquer containing alcohol, sandarac, turpentine resin and triphenyl phosphate and the whole is heated at 40--60 DEG  C. (red-violet).  (12) The dyestuff from 5-oxy-2 : 6-dichlorobenzaldehyde (1 mol.) and o-cresotinic acid (2 mols.) (cf. German Specification 244,826) is added with sodium bichromate and oxalic acid to a warm aqueous solution of gelatine and the whole is heated at 45--50 DEG  C. (blue).  (13) The dyestuff from 5 - oxy - 2 : 4 : 6 - trichlorobenzaldehyde (1 mol.) and o-cresotinic acid (2 mols.) (cf. German Specification 199,943) is added with sodium bichromate to a printing composition containing a lithographic varnish and ethyl lactate and the whole is heated at 70 DEG  C. for \ba1/2\be hour (blue).  (14) The dyestuff of (5) and sodium bichromate are added to a nitrocellulose lacquer and the whole is gently warmed (green).  (15) The leuco compound of (4) is replaced by the dyestuff itself and the oxalic acid is omitted (green).  (16) Naphthochrome blue BN and sodium bichromate are added to a nitrocellulose lacquer and the whole is gently warmed (blue).  (17) Naphthochrome green G and sodium bichromate are added to an acetylcellulose lacquer and the whole is gently warmed (brilliant green).  German Specifications 232,624, 285,323, and 462,221 also are referred to.  The Specification as open to inspection under Sect. 91 comprises also a further example in which the dyestuff of example 1 of German Specification 123,077 is added with sodium bichromate to a nitrocellulose lacquer and the whole is gently warmed (brilliant blue-red).  This subject-matter does not appear in the Specification as accepted.ALSO:Film-forming gelatine solutions are coloured by converting a mordant dyestuff of the triarylmethane series or a leuco compound thereof into a chromium compound of the dyestuff by treatment with chromic acid or a salt thereof in the solution itself. The colourations are especially fast to light.  In an example, the dyestuff from 5-oxy-2 : 6-dichlorobenzaldehyde (1 mol.) and o-cresotinic acid (2 mols.) (cf. German Specification 244,826) is added with sodium bichromate and oxalic acid to a warm aqueous solution of gelatine and the whole is heated at 45-50 DEG  C. to obtain a solution yielding on drying a blue film, very fast to light.